Use of ground-mounted highway and border markers is commonplace, as is use of systems and structures to allow such markers to survive impacts from vehicles while preserving the structural integrity and efficacy of the marker and minimizing the impact damage to the vehicle.
The type of marker being generally described is one that is mounted to a supporting surface (most commonly the ground, or the surface of a road or highway) and which extends above the ground to make the marker easily visible. Such visibility carries with it the considerable risk that, at one time or another, the marker will be struck by careless or inattentive drivers. Replacing each such marker as it is struck and broken represents a considerable expense in both manpower and material.
Accordingly, a number of systems have been proposed to protect the marker, or enable it to absorb such impacts, while also protecting the impacting body or vehicle. One such system involves the use of a marker having an easily sheared section which allows the marker to break easily under a relatively light impact. Such a solution requires frequent and immediate replacement of such markers, a situation which is manifestly unsuitable and dangerous where the markers involved were intended to mark off a highway or roadway boundary or hazard.
Exemplary of prior art efforts to provide a pivot which allows the marker post to yield to the force of impact and regain its upright orientation is U.S. Pat. No. 4,270,873, issued to Laehy, et al. Laehy teaches a two-piece telescoping tube construction having an internally disposed spring in the lowermost tube attached to an eye bolt supported by an anchor block in the uppermost tube. The two tubes pivot with respect to each other at the point where the upper spring tang is attached to the eye bolt.
In U.S. Pat. No. 1,282,673, issued to Brakery a deflectable sign post is shown having a coil spring element contained within the post itself with the lowermost portion of the spring anchored to a housing attached at ground level to a mounting plate.
U.S. Pat. No. 1,284,376, issued to Lehman, teaches a traffic indicator having an arcuate bottom tangentially meeting an arcuate upper surface of a base, with a spring disposed between the indicator and the base.
U.S. Pat. No. 1,679,623, issued to Olsen, teaches a signal post having a spring disposed in a below-the-ground tube attached at a hinge point to an upper post.
British Pat. No. 873,559, issued to Fraikin exemplifies a yieldable post having a spring element disposed within the post anchored at ground level, the compressive force of which holds the post in an upright position and returns the post to an upright position after it has been deflected.